技术问询：iText支持的PDF标准及5.5.10版本适配详情

Great question! Let's break this down clearly, since older version docs can be tricky to track down.

First, as a general rule, iText has long supported core PDF specifications along with several specialized standards for accessibility, archiving, and print workflows:

• Core PDF standards: PDF 1.0 through PDF 1.7 (including all incremental updates and extensions)
• Archiving standards: PDF/A-1a, PDF/A-1b, PDF/A-2a, PDF/A-2b, PDF/A-2u
• Print-focused standards: PDF/X-1a, PDF/X-3, PDF/X-4
• Accessibility standard: PDF/UA-1 (with proper configuration and usage)

Since you're specifically asking about 5.5.10—one of the later releases in the iText 5.x branch—here's the exact breakdown of what it supports:

• Core PDF: Fully supports PDF 1.7 (the final legacy PDF standard before PDF 2.0 was released). It handles all core features like annotations, form fields, embedded fonts, and multimedia content as defined in PDF 1.7.
• PDF/A: Supports PDF/A-1a, PDF/A-1b, PDF/A-2a, PDF/A-2b, and PDF/A-2u. Note that PDF/A-3 support was added in later iText versions, so 5.5.10 doesn't include that.
• PDF/X: Supports PDF/X-1a:2003, PDF/X-3:2003, and PDF/X-4:2010. It doesn't support the newer PDF/X-5 or later variants.
• PDF/UA: Partial support for PDF/UA-1. While it has the foundational tools to create accessible PDFs (like tagging, proper alt text, and structure elements), you'll need to follow best practices manually—some automated accessibility checks and features were refined in later iText versions.
• Other standards: It also supports basic compliance with PDF/ECMA-320, and can generate PDFs compatible with ISO 32000-1 (the formal ISO standard for PDF 1.7).

One thing to keep in mind: iText 5.5.10 is an older release (launched in 2016), so it doesn't support PDF 2.0 (released in 2017) or any standards that came after that version's launch.

内容的提问来源于stack exchange，提问作者Radek Kantor